1. Field of the Invention
The present invention generally relates to strain relief devices for protecting cable end portions, and in a preferred embodiment thereof, more particularly relates to an improved strain relief device for protecting such cable end portions from damage due to both bending and torsional forces imposed thereon.
2. Description of Related Art
To protect the end portions of electrical cables and the like against damage thereto arising from flexural forces imposed thereon, it is now a common practice to attach to such cable end portions small devices known as "strain reliefs". The typical strain relief that is conventionally utilized in this protective application is generally of an elongated tubular configuration, coaxially receives the cable end portion to be protected, and resiliently flexes in response to bending forces imposed on the cable end to function as a shock absorber of sorts that resiliently resists cable end bending. Conventional strain reliefs of this general type are widely used on a variety of electrical products to which a power supply cable is operatively connected, such as a power hand tools, irons, toasters, computer components and the like.
While the resiliency of the typical cable strain relief of conventional construction generally does a creditable job of protecting its associated cable end portion from flexure damage, the conventionally configured strain relief is typically subject to a variety of well-known problems, limitations and disadvantages. For example, tubular strain reliefs with a uniform annular cross-section along their lengths provide an undesirably nonlinear resistance to transverse bending loads upon the cable end portion which they encircle. To achieve a more desirable, generally linearly progressive resistance to such transverse bending loads on the cable end portion, the bodies of many conventional strain reliefs have been given a conically tapered configuration along their lengths in an attempt to provide this progressive bending resistance along the length of the strain relief.
While this tapered body configuration tends to yield the desired progressive bending resistance, it is often the case that the conventional strain relief of this axially tapered body configuration rather loosely receives its associated cable end portions. Accordingly, this type of conventional strain relief does not protect its associated cable end portion from torsional twisting loads imposed thereon--the cable end portion can be simply twisted about its axis relative to the outwardly encircling strain relief.
In an attempt to solve this problem, various conventional strain reliefs having axially tapered bodies have been fixedly secured in one manner or another to the outer side surface of the cable end portion which they are designed to protect. When fixedly secured to the cable end portion in this manner, the axially tapered strain relief resiliently resists twisting loads imposed upon the cable end portion. However, unlike the transverse bending resistance that the strain relief provides, the torsional twisting resistance that it provides is not linearly progressive along its length. Stated otherwise, the rate of increase of the axial length of the strain relief body being twisted in response to, for example, a uniformly increasing torsional load on the cable end portion slows considerably. Accordingly, the torsional "stiffness" along the length of the tapered strain relief body does not, as would be desirable, linearly track the increasing torsional load on the cable end portion.
From the foregoing it can be seen that it would be desirable to provide a cable stain relief device which, in a generally linearly progressive manner along the strain relief length, resiliently resists both torsional and transverse bending loads imposed upon the cable end portion to which the strain relief is operatively attached. It is accordingly an object of the present invention to provide a strain relief device having these dual protective characteristics.